This invention relates to electrophoresis.
Electrophoresis, in which entities are moved through a medium as a result of an applied electric field, has become an increasingly indispensable tool in biotechnology and related fields. In electrophoresis, the electrophoretic medium through which the entities are moved is housed in an electrophoretic chamber. A variety of different chamber configurations find use, including slab gel holders, columns or tubes, microbore capillaries, grooves or channels on a substrate surface etc., where advantages and disadvantages are associated with each particular configuration.
The particular material from which an electrophoretic chamber is fabricated can have a significant impact on the results of the application in which the chamber is employed. Some materials, e.g., fused silica, have charged surfaces under conditions of electrophoresis which give rise to electroosmotic flow. The presence of electroosmotic flow (EOF) can change the movement profile of the entities through the medium during electrophoresis. Certain materials can also adsorb entities from the medium, such as proteins and other biomolecules, which can adversely affect the results of a particular application.
As knowledge of the effect of surface properties on the movement of entities through a medium in electrophoretic applications grows, there is an increasing interest in the development of methods to tailor the surface properties of the electrophoretic chamber to meet the needs of a particular application. For example, it may be desirable to have a surface modified to reduce or enhance EOF through the chamber, to reduce or enhance analyte adsorption to the walls of the chamber, to provide for stable attachment of a gel network to the surface of the chamber, and the like.
Although fused silica has traditionally been the material of choice from which electrophoretic chambers are fabricated, of increasing interest as an alternative material are plastics. Various means have been developed for the surface modification of materials employed in electrophoretic applications. Surface modification techniques that have been employed include techniques based on the physical or chemical alteration of the material surface, e.g., etching, chemical modification, and coating a new material over the existing surface, e.g., solvent coating or thin film deposition by chemical or vapor deposition, radiation grafting, chemical grafting and RF-plasma. The particular surface modification means employed necessarily depends on the material to be modified. For methods specifically directed to the treatment of plastic surfaces of electrophoretic chambers, see EP 665 430 A1 and EP 452 055 B1.
Despite the availability of a number of different plastic surface modification techniques, there is a continued interest in the development of new surface modification procedures which would increase the number of different available methods and provide for further surface property tailoring opportunities to best meet the needs of a particular application.
U.S. Pat. No. 4,680,201 describes a method for covalently attaching a polyacrylamide surface layer to the inner surface of fused silica capillaries. U.S. Pat. No. 5,433,898 describes a process for preparing material for use in the construction of contact lenses comprising two or more polymers.
EP 665 430 A1 and EP 452 055 B1 describe use of surface modified polymeric capillaries in electrophoresis.
Additional references describing electrophoresis in various surface modified capillaries include: Gilges et al., "Capillary Zone Electrophoresis Separations of Basic and Acidic Proteins Using Poly(vinyl alcohol) Coatings in Fused Silica Capillaries," Anal. Chem. (1994) 66:2038-2046; Rohlicek et al., "Determination of the Isoelectric Point of the Capillary Wall in Capillary Electrophoresis, Application to Plastic Capillaries," J. Chrom. A. (1994) 662:369-373; Schuitzner & Kenndler, "Electrophoresis in Synthetic Organic Polymer Capillaries: Variation of Electroosmotic Velocity and .zeta. Potential with pH and Solvent Composition," Anal. Chem. (1992) 64: 1991-1995; Nielen, "Capillary Zone Electrophoresis Using a Hollow Polypropylene Fiber," J. High Resolution Chrom. (1993) 16:62-64; and Liu et al., "Polymeric Hollow Fibers for Capillary Electrophoresis," J. Microcol. Sep. (1993) 5:245-253; Hjerten, "High Performance Electrophoresis Elimination of Electroendosmosis and Solute Adsorption," J. Chromatogr. (1985) 347:191-198.
Encyclopedia of Polymer Science and Engineering, "Adhesion and Bonding," Vol. 1, pp. 476 et seq. (Wiley Interscience, 1985) describes reactive adhesives based on the surface interpenetration of reactive monomers.
A review of surface modification of polymer materials is provided in Ratner, Biosensors & Bioelectronics (1995) 10:797-804.